高速公路改扩建上跨铁路非对称转体桥梁设计

Design of Asymmetric Rotation Construction of a Railway Overpass on a Reconstructed Expressway

滨莱高速公路改扩建工程上跨铁路立交桥为(50+85+50)m连续梁桥,主梁采用单箱三室变截面箱梁,受现场条件限制,采用非对称转体施工,转体时两侧转体悬臂长度相差9 m。主墩采用变截面实体墩,边墩采用柱式桥墩,基础采用群桩基础。在主墩墩底设转体系统,通过对转体桥梁下部结构分析,确定施工过程中容许不平衡弯矩为5.18×10^(4) kN·m。设计将箱梁非对称长度单独分段,并采用混凝土块配重方式消除施工过程中的不平衡弯矩,对施工步骤进行优化,确定采用分次施加和拆除配重的方式。该桥采用优化后步骤施工,称重后现场单个转体配重重量为9600 kN,墩底不平衡弯矩实测值与理论值吻合较好,实际施工过程中最大不平衡弯矩为5.02×10^(4) kN·m,成功完成转体,保证了结构的安全。

The railway overpass of the Binzhou-Laiwu Expressway reconstruction project is a continuous beam bridge with three spans of 50,85 and 50 m.The superstructure consists of three-cell box beams of variable cross-section.Limited by the construction space,an asymmetric rotation construction solution was selected.The two cantilevers rotated were not in same length,with one 9 m longer.The main piers are solid piers of variable cross-section,while the side piers are column piers,and all the piers are supported by group pile foundations.The swivel system was installed beneath the main pier base.The allowable unbalanced bending moment during the construction could reach up to 5.18×10^(4) kN·m,according to the analysis of the substructure.To address the unbalanced bending moment,the extra length of the cantilever rotated was treated as an independent section and filled with concrete blocks for counterbalance,and the concrete blocks were added and demolished in stages to facilitate the construction.After optimization of the construction sequence,the counterweight in a single cantilever was 9600 kN,the measured and theoretical unbalanced pier-base bending moments were in good agreement.In the actual construction process,the maximum unbalanced bending moment was 5.02×10^(4) kN·m.The rotation construction was performed smoothly and the structure safety was guaranteed.